The Nazis established six extermination camps on Polish soil. These were Chelmno<span> (</span>December 1941-January 1945), Belzec (March-December 1942), Sobibor (May-July 1942<span> and </span>October 1942-October 1943), Treblinka (July 1942-August 1943), Majdanek (September 1941-July 1944) and Auschwitz-Birkenau (March 1942-January 1945<span>) ...</span>
You did not include any answer choices but I think I have run across this question before and remember the answer. I believe it is the "Land Act of 1800."